What was found
INSPECTION TYPE:N/A, AFTER LANDING GEAR HANDLE SELECTED UP, A LARGE BANG WAS HEARD WITH A FOUL SMELL THROUGHOUT THE COCKPIT, NO OTHER ABNORMAL INDICATIONS. EMERGENCY DECLARED WITH CENTER CONTROLLER. INSPECTED AIRCRAFT FOR DAMAGE CHECKED INLETS FOR FOD AND BIRDS. RAN PACKS AND CHECKED FOR LEAKS AND ODOR, NO SMELL NOTED. AIRCRAFT STILL NEED GEAR SWING. FOUND RIGHT DUCT BLOWN OFF AFT OF COALESCER ASSY. RE-ATTACHED DUCT, GEAR OPS CHECK NORMAL.